In a typical vortex injector used in conjunction with an engine in whose combustion chamber hypergolic ignition occurs, mass flow control is accomplished in one of two ways. One approach is to utilize throttling valves that are positioned outside of the fuel supply manifold such that the flow is regulated at a place other than the entrance to the injection orifices. This approach is simple to implement but high throttling ratios (maximum mass flow-rate divided by minimum mass flow-rate) cannot be achieved via this approach without significant losses in engine performance. The losses occur because the minimum allowed pressure drop across the injection orifices is not maintained at the entrance to the orifices. The only way to overcome these losses is to employ a configuration that closely couples the throttling mechanism to the injection orifices.
The second approach to maintaining mass flow control does employ close coupling of the throttling mechanism to the injection orifices. However, this approach requires a breaching of the fuel manifold and using either an electrical or pneumatic actuator to drive the throttling mechanism via a mechanical link that passes through the breach. A significant disadvantage of this method is the requirement for a robust sealing system at the manifold-to-mechanical link interface, giving rise to reliability issues.